Microphone no longer detected in the middle of meetings and video freezes

Check your computer's error log after this happens to see if you can find a report for a problem occurring at the time Zoom freezes on you.  (You can do this by going to Control Panel>System and Security>Security and Maintenance>Problem Reports.)  Another option is to check the Reliability Monitor.  You should be able to find the times that Zoom stopped responding for you, and you can then check back through reports to see if there are other problems occurring at the same time.  When I did this, I found that I was also having problems with Adobe Acrobat.  It hadn't installed correctly, so I uninstalled and reinstalled it. 

You might also get some insight by checking the Task Manager, but that's not convenient if you're in or trying to join a meeting. 

I've stopped using my Dell for Zoom and rely instead on my Chromebook.  I think the Dell has too many extra things running in the background.  At some point, I'll take the laptop to my university's help desk to see what I can do without.  I think when I bought this machine Dell loaded it with a bunch of stuff I don't really want or need, like Microsoft Edge and other Microsoft products.  Too many bells and whistles, but that's a rant for another day.